Re: BYO CNC Lathe ?

Chris,

Linear rails are perfectly acceptable for a small lathe or mill.
Many of the production machine tool manufacturers offer their lower
end machines with linear rails. See Fadal, Mori-Seiki, etc (these
machines would be considered extremely high end compared to what most
of the list members have). Their higher end, more rigid machines
have solid box ways. The linear rail machines are noticeably less
expensive.

Linear rail machines are sometimes sarcastically referred to
as "roller skate" machines since they can very seldom ever reach the
rigidity of solid ways. But, in the size range you're considering
properly selected rails would be a very good alterative to trying to
convert a low cost piece of poorly made cast iron.

By designing from scratch with linear rails you have the major
advantage of being able to design so your lead screws are in the best
location rather than having to work around the casting of a machine
meant to be used manually.

My Accuslide CNC conversion on a Hardinge chucker uses 25mm rails.
I part off 1"SS bar which is a very good test of a machine's rigidity.

Doug

--- In CAD_CAM_EDM_DRO@y..., Chris L <datac@l...> wrote:
> Ok,
> I've taken an interest in purchasing a small lathe to convert to
CNC.
> Everything I look at though, spooks me off a bit. The Taig...To
Small.
> The Sherline, To Pricey. The Imports ? Well, we picked up a Jet
9x20 for
> a quick and dirty machine and I was not very impressed. I did not
think
> one should build a machine like that out of such soft metal. You
should
> see how wobbled out the wrench holes are in the spindle from taking
the
> chuck off ! Scary! I do not think I would ever cnc that thing.
>
> So, I began to think about building my own. (BYO)
> Is there any reason why I could not use some good sized THK-IKO
style
> bearings for the rails ? Why do all lathes have the typical beds
with
> sliding gib concepts anyhow ? Linear bearings should work, No ?
>
> I could even put the Tailstock on the same rails with a separate
> leadscrew and handwheel instead of having the tailstock made in the
> conventional way. That sounds alright.
>
> I could come up with a really neat spindle with a really large thru
hole
> instead of all this too small stuff. (I knew I would someday find a
use
> for front wheel drive cars... The front hub and spindle ! I could
keep
> my GM lathe ALL GM !)
>
> I thought I could probably use big chunks of Billet aluminum for the
> headstock and tailstock but was worried about not getting enough
mass.
> But I suppose it would still be as good as a Taig or Sherline.
>
> Thoughts ? Am I nuts ?
>
> Chris L